Method for maintaining an aqueous solution of sodium borate in a liquid form at room temperature

Abstract

A method of keeping an aqueous solution of sodium borate liquid at a storage temperature, in which method, in order to pass said solution from an initial temperature to the storage temperature, said aqueous solution of sodium borate is subjected to heat treatment comprising at least one cooling or heating operation at a speed lying in the range 1° C./min to 100° C./min, to reach a holding temperature lying in the range −50° C. to +200° C., followed by holding the holding temperature for a time lying in the range 1 s to 100 h, followed by cooling or heating at a speed lying in the range 1° C./min to 100° C./min. Use of the method in a method of supplying hydrogen for a fuel cell.

1 . A method of keeping an aqueous solution of sodium borate liquid at a storage temperature, in which method, in order to pass said solution from an initial temperature to the storage temperature, said aqueous solution of sodium borate is subjected to heat treatment comprising at least one cooling or heating operation at a speed lying in the range 1° C./min to 100° C./min, to reach a holding temperature lying in the range −50° C. to +200° C., followed by holding the holding temperature for a time lying in the range 1 s to 100 h, followed by cooling or heating at a speed lying in the range 1° C./min to 100° C./min.  
   
   
       2 . A method according to  claim 1 , wherein the heat treatment includes at least two holding operations at different holding temperatures.  
   
   
       3 . A method according to  claim 1  or  claim 2 , wherein, prior to performing the heat treatment, the aqueous solution of sodium borate is at an initial temperature lying in the range 100° C. to 180° C., and after performing the heat treatment, the aqueous solution of sodium borate is at a storage temperature lying in the range −50° C. to +300° C.  
   
   
       4 . A method according to  claim 3 , wherein the storage treatment lies in the range −20° C. to +50° C.  
   
   
       5 . A method according to  claim 1 , wherein the aqueous solution of sodium borate contains 5% to 65% by weight of sodium borate.  
   
   
       6 . A method according to  claim 5 , wherein the aqueous solution of sodium borate further contains 0% to 10% by weight of soda.  
   
   
       7 . A method of generating hydrogen in which sodium borohydride is caused to react with water and both a gaseous mixture constituted mainly of hydrogen and an aqueous solution of sodium borate are extracted therefrom, wherein the aqueous solution of sodium borate is subjected to the method according to  claim 1 .  
   
   
       8 . The use of the method of  claim 7 , comprising feeding hydrogen to a fuel cell.  
   
   
       9 . The method of  claim 8 , wherein the fuel cell is the fuel cell of a motor vehicle.  
   
   
       10 . The method according to  claim 7  wherein the hydrogen is used in medicine, in the agrifood industry, in the fabrication of electronic components, and/or in the implementation of heat treatments on metal products.